If you have an email address then you can use Thunderbird as an email client to view emails. You will need to know what server settings are used by the server which offers the email address eg: Outlook, gmail, BT, comcast, xfinity, ionos etc.

You may need to logon to webmail account via a browser and select to enable Imap (or Pop if prefered).

In Thunderbird 'click on the app icon which has 3 lines and select 'New Account' > 'Email Enter your name, email address and password. Select the checkbox to remember password and click on 'Continue'

You may need to click on 'Manually Configure' and adjust the settings as not all server configurations are known.

If you cannot use Imap or Pop or smtp because your admin has disabled it and perhaps you are connecting to eg: Microsoft Exchange then there is an addon which you could use. Please note it is a paid for addon bt the annual price is very small. https://addons.thunderbird.net/en-us/thunderbird/addon/owl-for-exchange/

Be aware that most server do not like VPN. Disable VPN or create a tunnel for Thunderbird application

If using Outlook, Yahoo or gmail then authentication Method uses Oauth, so you need to ensure the following.

If you use any application which uses 'localhost' eg: Apache Xampp then switch it off whilst setting up the Oauth token.

Thunderbird needs to have cookies enabled in order to communicate with server login. In Thunderbird Settings > Privacy & Security Under 'Web Content' Select 'Accept cookies from sites' Accept third party cookies: Always